Mixing flowers and herbs with fruit and vegetables is one of the cornerstones of companion planting. It has been practised by gardeners for centuries, and has increased in popularity as organic growing methods have become more well-known. It also looks wonderful, whatever style of edible garden you favour, whether it be the traditional cottage garden or the formal potager.

Companion planting is a natural and highly expedient method of cultivation involving the grouping together of plants that make good neighbours. It avoids monoculture in favour of working in harmony with nature. Having a mixed natural growing system provides greater biodiversity, which in turn creates much more stability and resilience in the face of changing conditions. In nature, plants grow in close communities with a number of different species existing side by side – unlike the rigid rows of single crops found in many vegetable gardens – and companion planting can provide specific benefits to vegetables, fruits, herbs and ornamentals.

The benefits start with the natural control of pests and diseases. Many flowering plants – most members of the daisy family, for instance – will attract predatory insects such as hoverflies and ladybirds, both of which will consume aphids. The odour produced by certain plants can deter many pests, such as whiteflies and aphids. Odoriferous plants, including those with aromatic oils, can play an important part in determining which insects visit the garden. For example, hemp can be used to repel the cabbage white butterfly. Other strongly scented plants, such as sweet basil, lemon balm, thyme and mint, work by simply confusing pests, many of which are lured to their target by scent alone.

The right choice of companion plant can also help to control competing plants. Many species of plant can reduce competition by effectively poisoning any other plants that try to grow nearby, so that they remain the dominant species. The walnut tree is a good example; it produces the poisonous chemical juglone and is therefore not threatened by any competing vegetation, including its own seedlings. Mexican marigold Tagetes minuta makes an excellent companion plant; its root secretions can assist in killing ground elder and bindweed and it is also effective in nematode control.

Some companion plants can greatly assist in improving the soil. For example, flax will break up a clay soil. Mustard produces alkaline secretions from its roots and can be used as a green manure or cover crop to prepare an acid soil for a subsequent crop which prefers alkaline conditions.

Many plants in the legume family, such as peas, beans and clovers, possess the ability to “fix” nitrogen from the atmosphere for their own and neighbours’ use. What is not used is left in the soil for the benefit of subsequent crops. The addition of clover to grass mixtures is an old farming practice. Clover can also be interplanted amongst sweetcorn, which will benefit from the clover as a ground cover. The clover can be left after the corn has been harvested to protect the soil during the winter. In the spring it can be dug into the ground, where its nutrients will be released to feed other plants.

Planting insect-attracting companion plants among your crops will improve pollination. Bees love the fragrance of herbs such as lemon balm, thyme, sweet basil, mint, summer savory, flowering parsley and many more. If you plant any of these near vegetable crops which depend on a good rate of pollination, such as beans, it will help to ensure that the flowers “set” and produce a good crop.

Growing a mixture of plants together helps to create a diverse habitat capable of supporting a wide range of insects. These in turn will prey on the more common pests. Growing a range of flowering “attractant” plants will encourage ladybirds, hoverflies, lacewings and other beneficial insects. This will achieve a reduction in crop damage and allow you to eliminate pesticide use.

Companion plants can also act as sacrificial crops. The idea is to grow certain plants to attract insect pests so that they leave your crop plants alone. For example, aphids prefer nasturtiums to other plants. However, this is a risky undertaking as insect populations tend to rise in response to the available food supply. Once their favourite plants are exhausted, they will then move on to other plants – so it is important to ensure a continuous supply of the sacrificial plants.

Another role that companion plants can play is that of “nurse” crops. Many plants require protection from wind and excessive sunshine. There are many edible plants that can provide this, like Jerusalem artichokes, which can grow to two metres tall. Some plants can provide one another with mutually beneficial physical conditions. For instance, pumpkins or courgettes can keep the ground moist and shaded, which suits sweetcorn, while the pumpkins or courgettes appreciate the support and partial shade provided by the corn. Native Americans always grew beans, squash and sweetcorn together – these were known as the “three sisters”. The dense prickly squash leaves deter animal invaders; the corn offers the beans the support they require; and the beans repay this by fixing nitrogen in the soil for all three plants.

It is not always clear why specific instances of companion planting work. Some are not (and may never be) scientifically proven – but it is a fact that this method of gardening produces happier plants and provides better insect control than monoculture. Companion planting can be worked into any style of edible gardening, whether it is the informality of the cottage garden, with its riotous bevy of intermingled fruit, flowers, herbs and

vegetables, or the formality of the traditional vegetable garden, where rows of vegetables can be separated by strips of companion herbs, or surrounded by flowers.

Do not get bogged down in the myriad possibilities of companion planting. Simply growing a wide range of plants, both edible and non-edible, is the best method for the health of the whole garden, as it helps to provide a diverse habitat for a wide range of insects, both good and bad. Chances are the natural system will then sort it all out!

Monoculture, as practised in intensive commercial gardens, on farms, and in many non-organic private gardens, creates a pest and disease paradise, and in the absence of any natural predators, growers reach for the spray gun. A garden buzzing with bees, butterflies and insects feels alive in a way that a pesticide-controlled plot of land never can. So go and enjoy seeing your companions hard at work on your behalf in your garden, and listen to nature all around you.

Biog: Michael Littlewood is a landscape designer and the author of many gardening publications including The Organic Gardener’s Handbook.

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Companion Planting Chart

Michael Littlewood’s beautifully illustrated full-colour charts, guides and calendars provide a wealth of information for your gardening year – and they make perfect gifts for any keen gardener. All are produced by an environmentally friendly printing process, using paper from sustainable sources, and are packed in biodegradable tubes.

A Guide to Companion Planting

‘Two little books which both promote the philosophy of gardening in harmony with nature have been published by landscape designer and organic gardener Michael Littlewood… These easy-read, attractive and beautifully illustrated guides… (are) for those who want a simple and straightforward guide to these subjects. A Guide to Companion Planting is… a beginners’ guide providing a straightforward introduction to the basics of how companion plants work to make for a healthier and more productive garden. It promises to make companion planting accessible and achievable.’ Kitchen Garden, April 2010